The present invention relates to a radiation image detecting apparatus having its radiation receiving section made up of arrayed radiation sensors.
In a method of electronically detecting a radiation image, the radiation receiving portion consists either of a one-dimensionally arrayed radiation sensors devised so as to scan an image plane or of a two-dimensionally arrayed sensors fixed at an image plane. Each of the radiation sensors is either a single semiconductor sensor or a radiation scintillator combined with a photosensor. In any case each sensor, which converts the radiations incident thereon to electric pulse signals, is followed by an amplifier, a signal discriminator and a counter. The counter counts the number of the pulse signals (pulses) outputted from the counter in the form of a digital signal. Similar radiation intensity signals from all of the counters belonging the arrayed radiation sensors are purposefully treated by a common picture-signal forming circuit, which provides a picture signal to a CRT to make it display a radiation image. Radiation image detecting apparatus based on such a method as mentioned above are disclosed, for example, in the Japanese Laid-open Patent Application No. 59-94046 and European Patent Publication EP-O-137-487-A2.
The apparatus so devised as mentioned above have an important problem to be solved in regard of protecting the constituent circuits from being unfavorably affected by the heat dissipated by the circuits themselves. Suppose that the power consumption per sensor consists of 140 mW at the amplifier, 100 mW at the signal discriminator and 10 mW at the counter, making a total of 250 mW. A one-dimensional array of 1000 sensors, for example, causes an overall heat dissipation of 250 W. This value estimated with 1000 sensors supposed may further increase by several times to some hundred times or more, if the sensors are increased in number for making the image resolving power higher or for constituting the arrayed sensors in two-dimension. In case the radiation image to be detected is, for instance, an X-ray image for diagnosis, one shot of the detection takes only one second or less, and therefore, if a very small number of images are enough for the diagnosis, there is no problem in substance. It is, however, not rare that several tens of images are needed for the diagnosis of one desease. In such a case, if competent measures are not provided to protect the circuits from the heat effect, a series of the X-ray image detection work must be interruppted frequently for cooling the circuits. This not only lowers the efficiency of the image detection work but also keeps the patient under an unpleasant condition for a long time.